A conventional optical head device which is used for reproducing information from an optical disk such as a CD or a DVD includes a laser beam emitting element, an objective lens drive mechanism which is provided with an objective lens for converging a laser beam emitted from the laser beam emitting element on an optical disk and is driven in a focusing direction and in a tracking direction, a light receiving element which receives a return light reflected by the optical disk, and parts for an optical system for guiding the laser beam between the laser beam emitting element and the light receiving element. These optical parts are mounted on a base.
As shown in Japanese Patent Laid-Open No. 2004-192720, a conventional frame type of laser beam emitting element 2 is held with a light emitting element holder 9 which is formed of a first holder member 91 and a second holder member 92 abutting with fins 24a, 25a from both sides to hold the laser beam emitting element 2 and is adhesively fixed to the base 10.
When the light emitting element holder 9 is to be adhesively fixed to the base 10, the position of an emitted light point of the laser beam emitting element 2 is required to be adjusted in a three-dimensional direction. Therefore, the light emitting element holder 9 and the base 10 are adhesively fixed to each other through a gap space in which the position of the emitted light point of the laser beam emitting element 2 can be adjusted in a three-dimensional direction.
With the speeding-up of disk dive device operation in recent years, the amount of heat generated in the laser beam emitting element 2 is also increased. In addition, with the miniaturization and thinning of an optical head device, since the light emitting element holder 9 of the laser beam emitting element 2 is downsized, heat radiation can not be sufficiently performed by only the heat radiating fins 24a, 25a. In order to solve the problem, for example, it is conceivable that the light emitting element holder 9 is formed of material, which is excellent in heat conductive property, to radiate heat from the heat radiating fins 24a, 25a to the light emitting element holder 9. However, with the miniaturization and thinning of an optical head device, since the light emitting element holder 9 is downsized, heat radiation can not be performed sufficiently even when such the light emitting element holder 9 is used. In the light emitting element holder 9 described in the above-mentioned patent reference, a gap space is provided between the light emitting element holder 9 and the base 10 so as to be capable of adjusting the position of the emitted light point of the laser beam emitting element 2 in a three-dimensional direction. Therefore, since heat radiation can not be sufficiently performed to the base 10 from the light emitting element holder 9, temperature of the laser beam emitting element 2 becomes higher and thus a service life time of the laser beam emitting element 2 maybe shortened.
Further, another conventional optical head device which is used for reproducing information from an optical disk such as a CD or a DVD includes an optical system having a laser beam emitting element as a light source, a laser driver integrated circuit (laser driver IC) for driving the laser beam emitting element, a frame on which the optical system is mounted, a cover fixed to a frame for protecting the optical system and the like.
In this optical head device, the cover for protecting the optical system is commonly formed of a metal plate made of stainless steel and heat generated in the laser driver is radiated through the cover. In other words, in a conventional optical head device, a cover which functions as a heat sink for a laser driver is used. A conventional structure of the optical head device will be described with reference to FIGS. 15 and 16.
As shown in FIG. 15, an optical head device 101 includes a laser beam emitting element 102 as a light source, a laser driver IC 104 mounted on a circuit 103 for driving the laser beam emitting element 102, and a frame 105 on which an optical system including the laser beam emitting element 102 is mounted. Further, as shown in FIG. 16, a cover 106 formed of a stainless-steel plate is fixed to the frame 105 with a mounting screw 108 to protect the optical system.
As shown in FIG. 16, the cover 106 is fixed so as to cover almost the whole portion of a bottom face side of the frame 105, and optical elements structuring the optical system is covered by the cover 106. The cover 106 contacts with the laser driver IC 104 through a heat transmission sheet (not shown) which is provided with heat transmission property and elasticity. Therefore, heat generated in the laser driver IC 104 is radiated to the frame 105 through the heat transmission sheet and thus the cover 106 functions as a heat sink for the laser driver IC 104.
A method for positively radiating heat generated in the laser driver IC is disclosed in Japanese Patent Laid-Open No. 2004-192751, in which a laser driver IC is disposed on an optical disk side and air is circulated by rotation of the optical disk to radiate the heat generated in the laser driver IC to the air through a heat radiation member.
When the conventional optical head device 101 is structured as shown in FIG. 16, since the cover 106 functions as a heat sink for the laser driver IC 104, temperature of the cover 106 rises with rising of the temperature of the laser driver IC 104. The cover 106 covers almost the whole portion on the bottom face side of the frame 105 on which the optical system is mounted and thus the temperature of the whole frame 105 also rises with rising of the temperature of the cover 106. Further, with rising of the temperature of the cover 106, temperature of the optical elements which are covered by the cover 106 also rises.
With higher-density recording and speeding-up for an optical disk in recent years, the amount of heat generated in the laser driver IC 104 which drives the laser beam emitting element is increased. On the other hand, with the miniaturization and thinning of an optical head device, the heat sink is also downsized. Therefore, the temperature of the whole frame 105 rises and the temperature of the optical elements covered by the cover 106 becomes higher and thus optical characteristics of the optical head device 101 are affected. In other words, fixed positions of the optical elements structuring the optical system are displaced by temperature rising of the frame 105 and thus optical characteristics of the optical head device 101 are affected.
Further, in the latter patent reference, adverse effects to the optical elements may be avoided by a laser driver IC which is arranged on an optical disk side and heat is radiated through a heat radiation member which is a different member from the cover. However, in this patent reference, the heat radiation member which is provided with both arm portions facing each other in a jitter direction is formed in a U-shape so as to avoid an actuator (objective lens drive mechanism). Therefore, although its outer shape is large, a sufficient heat radiation area is not obtained and thus heat radiation effect is not satisfactory. Further, a dedicated heat radiation member for the laser driver IC is required separately and thus the number of parts is increased. In addition, in a thin-type of optical head device used in a notebook-sized personal computer or the like, the heat radiation member is not exposed from an opening of a tray on which an optical disk is placed and thus cooling effect is not sufficient.